mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-21 10:33:27 +00:00
263 lines
10 KiB
Rust
263 lines
10 KiB
Rust
use crate::utils::{
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eq_expr_value, get_trait_def_id, implements_trait, snippet_opt, span_lint_and_then, trait_ref_of_method,
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};
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use crate::utils::{higher, sugg};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::hir::map::Map;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for `a = a op b` or `a = b commutative_op a`
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/// patterns.
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///
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/// **Why is this bad?** These can be written as the shorter `a op= b`.
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///
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/// **Known problems:** While forbidden by the spec, `OpAssign` traits may have
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/// implementations that differ from the regular `Op` impl.
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///
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/// **Example:**
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/// ```rust
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/// let mut a = 5;
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/// let b = 0;
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/// // ...
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/// // Bad
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/// a = a + b;
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///
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/// // Good
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/// a += b;
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/// ```
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pub ASSIGN_OP_PATTERN,
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style,
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"assigning the result of an operation on a variable to that same variable"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for `a op= a op b` or `a op= b op a` patterns.
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///
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/// **Why is this bad?** Most likely these are bugs where one meant to write `a
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/// op= b`.
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///
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/// **Known problems:** Clippy cannot know for sure if `a op= a op b` should have
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/// been `a = a op a op b` or `a = a op b`/`a op= b`. Therefore, it suggests both.
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/// If `a op= a op b` is really the correct behaviour it should be
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/// written as `a = a op a op b` as it's less confusing.
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///
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/// **Example:**
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/// ```rust
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/// let mut a = 5;
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/// let b = 2;
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/// // ...
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/// a += a + b;
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/// ```
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pub MISREFACTORED_ASSIGN_OP,
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complexity,
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"having a variable on both sides of an assign op"
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}
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declare_lint_pass!(AssignOps => [ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP]);
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impl<'tcx> LateLintPass<'tcx> for AssignOps {
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#[allow(clippy::too_many_lines)]
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
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match &expr.kind {
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hir::ExprKind::AssignOp(op, lhs, rhs) => {
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if let hir::ExprKind::Binary(binop, l, r) = &rhs.kind {
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if op.node != binop.node {
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return;
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}
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// lhs op= l op r
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if eq_expr_value(cx, lhs, l) {
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lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, r);
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}
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// lhs op= l commutative_op r
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if is_commutative(op.node) && eq_expr_value(cx, lhs, r) {
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lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, l);
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}
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}
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},
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hir::ExprKind::Assign(assignee, e, _) => {
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if let hir::ExprKind::Binary(op, l, r) = &e.kind {
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let lint = |assignee: &hir::Expr<'_>, rhs: &hir::Expr<'_>| {
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let ty = cx.typeck_results().expr_ty(assignee);
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let rty = cx.typeck_results().expr_ty(rhs);
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macro_rules! ops {
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($op:expr,
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$cx:expr,
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$ty:expr,
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$rty:expr,
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$($trait_name:ident),+) => {
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match $op {
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$(hir::BinOpKind::$trait_name => {
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let [krate, module] = crate::utils::paths::OPS_MODULE;
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let path: [&str; 3] = [krate, module, concat!(stringify!($trait_name), "Assign")];
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let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
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trait_id
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} else {
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return; // useless if the trait doesn't exist
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};
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// check that we are not inside an `impl AssignOp` of this exact operation
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let parent_fn = cx.tcx.hir().get_parent_item(e.hir_id);
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if_chain! {
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if let Some(trait_ref) = trait_ref_of_method(cx, parent_fn);
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if trait_ref.path.res.def_id() == trait_id;
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then { return; }
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}
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implements_trait($cx, $ty, trait_id, &[$rty])
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},)*
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_ => false,
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}
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}
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}
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if ops!(
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op.node,
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cx,
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ty,
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rty.into(),
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Add,
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Sub,
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Mul,
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Div,
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Rem,
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And,
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Or,
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BitAnd,
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BitOr,
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BitXor,
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Shr,
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Shl
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) {
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span_lint_and_then(
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cx,
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ASSIGN_OP_PATTERN,
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expr.span,
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"manual implementation of an assign operation",
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|diag| {
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if let (Some(snip_a), Some(snip_r)) =
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(snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
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{
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diag.span_suggestion(
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expr.span,
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"replace it with",
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format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
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Applicability::MachineApplicable,
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);
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}
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},
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);
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}
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};
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let mut visitor = ExprVisitor {
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assignee,
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counter: 0,
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cx,
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};
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walk_expr(&mut visitor, e);
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if visitor.counter == 1 {
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// a = a op b
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if eq_expr_value(cx, assignee, l) {
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lint(assignee, r);
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}
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// a = b commutative_op a
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// Limited to primitive type as these ops are know to be commutative
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if eq_expr_value(cx, assignee, r) && cx.typeck_results().expr_ty(assignee).is_primitive_ty() {
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match op.node {
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hir::BinOpKind::Add
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| hir::BinOpKind::Mul
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| hir::BinOpKind::And
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| hir::BinOpKind::Or
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| hir::BinOpKind::BitXor
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| hir::BinOpKind::BitAnd
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| hir::BinOpKind::BitOr => {
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lint(assignee, l);
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},
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_ => {},
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}
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}
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}
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}
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},
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_ => {},
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}
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}
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}
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fn lint_misrefactored_assign_op(
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cx: &LateContext<'_>,
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expr: &hir::Expr<'_>,
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op: hir::BinOp,
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rhs: &hir::Expr<'_>,
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assignee: &hir::Expr<'_>,
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rhs_other: &hir::Expr<'_>,
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) {
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span_lint_and_then(
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cx,
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MISREFACTORED_ASSIGN_OP,
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expr.span,
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"variable appears on both sides of an assignment operation",
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|diag| {
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if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span)) {
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let a = &sugg::Sugg::hir(cx, assignee, "..");
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let r = &sugg::Sugg::hir(cx, rhs, "..");
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let long = format!("{} = {}", snip_a, sugg::make_binop(higher::binop(op.node), a, r));
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diag.span_suggestion(
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expr.span,
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&format!(
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"Did you mean `{} = {} {} {}` or `{}`? Consider replacing it with",
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snip_a,
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snip_a,
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op.node.as_str(),
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snip_r,
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long
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),
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format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
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Applicability::MaybeIncorrect,
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);
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diag.span_suggestion(
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expr.span,
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"or",
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long,
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Applicability::MaybeIncorrect, // snippet
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);
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}
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},
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);
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}
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#[must_use]
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fn is_commutative(op: hir::BinOpKind) -> bool {
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use rustc_hir::BinOpKind::{
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Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
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};
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match op {
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Add | Mul | And | Or | BitXor | BitAnd | BitOr | Eq | Ne => true,
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Sub | Div | Rem | Shl | Shr | Lt | Le | Ge | Gt => false,
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}
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}
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struct ExprVisitor<'a, 'tcx> {
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assignee: &'a hir::Expr<'a>,
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counter: u8,
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cx: &'a LateContext<'tcx>,
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}
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impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
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type Map = Map<'tcx>;
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fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
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if eq_expr_value(self.cx, self.assignee, expr) {
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self.counter += 1;
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}
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walk_expr(self, expr);
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}
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::None
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}
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}
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